1. Field of the Invention
This invention relates to an impact energy absorbing structure of vehicle body upper portion of an automobile, and in more particular, to a structure for absorbing an impact energy caused by a structural member such as a front pillar, a center pillar, a rear pillar, or a roofside rail by an interior trim material disposed with a space from the structural member inwardly of a passenger compartment and an energy absorbing material disposed in the space.
2. Description of the Related Art
There has been proposed a vehicle upper structure (Japanese Patent Appln. Public Disclosure No. 6-211088) comprising a pillar of a vehicle, a pillar garnish disposed with a predetermined space inwardly of a passenger compartment, and an energy absorber disposed in the space. In the impact energy absorbing structures, when impact force directed from the inward to the outward of the passenger compartment is exerted, the interior trim material is deformed, and with the deformation the energy absorber is deformed to absorb impact energy.
There is a fear that, depending on the direction of the impact force exerted on the interior trim material, the interior trim material slides against the energy absorber, the interior trim material slides together with the energy absorber against the inner panel or the interior trim material is opened, causing to be out of an energy absorbing characteristic.
The above-mentioned problem is concretely explained in the following, for example, with reference to a pillar of an automobile. An automobile pillar is generally formed to present a closed structure in its horizontal section by joining flanges respectively of an inner panel and an outer panel, and the rigidity of the flange joint portion is particularly made great. As one of countermeasures against an impact due to a load directed toward the flange joint portion, the energy absorbing structure shown in FIG. 11 can be considered. The countermeasure is intended that, when an impact receiving body 20 is subjected to a load in the direction A, in order to ensure a space S sufficient not to bring the impact receiving body 20 with a flange joint portion 22 of a pillar 21, a side portion 24 of a pillar garnish 23 is bent in its horizontal section to project inwardly and to dispose an energy absorber 25 between the pillar 21 and the pillar garnish 23. A terminal portion 26 of the side portion of the pillar garnish becomes approximately parallel to the direction A of the load, and is positioned with a gap 28 from an inner panel 27 of the pillar 21.
Suppose the impact receiving body 20 is subject to a load in the direction A, the impact receiving body 20 firstly gets into contact with the protruded portion 29 of the side portion 24 of the pillar garnish 23, and thereafter moves toward the pillar 21. During the movement, the side portion 24 of the pillar garnish 23 moves substantially in the same direction as the direction A of the load. As shown in FIG. 12, when the gap 28 is gone, and the end face of the terminal portion 26 of the side portion 24 of the pillar garnish 23 is brought into contact with the inner panel 27, the terminal portion 26 stands firm so as to maintain its configuration, so that the load rises like C.sub.1 in FIG. 10. The terminal portion 26 as well as the protruded portion 29 of the side portion 24 are rather stronger than other portions of the pillar garnish 23. However, with an increase in load, those portions 26, 29 are deformed so as to have the load shifted to a weaker portion of the pillar garnish 23, so that the load is shifted to another weaker portion when it exceeds a load limit, simultaneously moving the energy absorber 25 in the direction B. As a result, the load decreases like C.sub.2 in FIG. 10. And when the energy absorber 25 gets into the state shown by an imaginary line in FIG. 12, an energy absorbing function is lost, so that the impact receiving body 20 gets into contact with the flange joint portion 22 and the load rapidly rises like C.sub.3 in FIG. 10. The amount of energy absorption in this case is given by an area defined under C.sub.1, C.sub.2, C.sub.3 in FIG. 10, but it can be said that the area is smaller for the difference in load, and that in an energy absorbing structure as shown in FIG. 11 an efficient energy absorption cannot be attained.